1. Field of the Invention
This invention relates generally to an apparatus for detecting fluid leakage from a piping system. More particularly, the present invention relates to a piping system leakage detection apparatus which can be easily adjusted to monitor various rates of leakage downstream from the sensor. This invention has particular application to leak detection for residential water pipeline systems.
2. Description of the Related Art
Leakage is most apt to occur at two points in the lifetime of a piping system. Immediately after installation, a newly-installed piping system may be subject to mistakes in assembly, fitting problems, or simple infant mortality failures due to poor quality control. At the other end of the piping system life cycle, long use or external influences, such as shifting terrain, will eventually produce cracks, splits, and interstice in the piping system and attached accessories, such as valves, resulting in leakage of fluids through the cracks. In either case, leakage results in loss of the fluid, and possible danger to the public.
To deal with such a problem various devices and methods for detecting fluid leaks have been proposed. Most are complicated in nature and difficult to install. Furthermore, application of these devices is generally limited by specific environmental conditions. Other types of detection apparatus are limited in usefulness because their sensors must be placed in proximity to a suspected leak location. Therefore, if the leak does not occur near the sensor, it will remain undetected.
Some examples of the prior art include U.S. Pat. No. 3,874,222, issued to Ladd et al., for a pipeline leak detector, which makes use of temperature sensors placed along the length of a pipeline to detect leaks. This invention depends on the pipeline carrying a thermally unstable material, which is defined as material which, if released from the pipeline, would be at a temperature significantly different from that of the material surrounding the pipeline. The temperature sensing devices must be spaced close enough together along the line so that leaking material will not escape undetected. These sensors must also be positioned about the circumference of the pipeline so that, for example, if the pipeline carries gas and leaks in an upward direction, the sensors will not miss the escaping material. Similarly, if the leaking material is a liquid that tends to seep into the ground via gravity, then the temperature sensing elements must be located beneath the pipeline. This invention suffers from the requirement of sensor placement being sensitive to the actual location of the leak.
Another invention is disclosed by U.S. Pat. No. 3,864,960, issued to Fletcher et al., for an apparatus which monitors the integrity of vacuum seals. Its operation depends on the use of two matched thermistors. Each is mounted in a thermal cell, one exposed to the vacuum for reference, and the other exposed to both the vacuum and a detector chamber adjacent the seal being monitored. This invention suffers from dependence on a matched pair of sensors for leak detection.
U.S. Pat. No. 4,259,861, issued to Yamamoto et al., discloses a leak detector which is specifically directed toward the leakage of a substance, such as sodium, which will impinge on the sensor, while losing a good deal of its inherent heat to vaporization. The invention is aimed at counting individual particles of sodium, or in the alternative, toward measuring the total weight of sodium which has leaked out of the system. Such a device is not well suited to the detection of fluid leakage, but rather, to the detection of particles in a mist.
Other inventions, such as that disclosed by U.S. Pat. No. 4,336,708, issued to Hobgood et al., deal with the absolute location of leaks within a system. In this case, a portion of leaking pipe must be excavated before the invention can be applied. The instant invention is not directed toward the precise location of a leak, but rather, to the detection of a "leaking" condition as opposed to a "non-leaking" condition, somewhere in the system.
Finally, the invention disclosed by U.S. Pat. No. 4,529,974, issued to Tanaka et al. discloses a complex apparatus for leak detection which relies on a heated bridge element whose resistance will vary if subjected to the presence of leaking fluid. Again, this system depends on the proximity of the sensor itself to leaking fluid. If the fluid travels in a direction away from the sensor, the leak will never be detected.
Leak detection apparatus disclosed by the prior art tend to be complex, which makes them commercially impractical, or directed toward precise location of the leak itself, and not to simply detecting the existence of a leak. In addition, the ability to easily adjust such systems for various rates of leakage has not been addressed.